This invention relates to a liquid fuel-air-explosive (FAE) device and, more particularly, the invention is concerned with providing a second event (SE) explosion within the boundaries of the FAE cloud at the proper time.
The liquid fuel-air-explosive device operates by rapidly dispersing liquid fuel to form the largest detonable cloud possible for the amount of liquid fuel used and subsequently detonating the cloud by means of a high explosive source. The basic fuel-air-explosive (FAE) device includes a liquid fuel container, a burster charge and second event (SE) cloud detonators. Detonation of the burster charge distributes the liquid fuel and SE detonators into what is called the FAE cloud. The SE detonators, in turn, initiate the fuel cloud creating the fuel-air-explosion.
After the dynamic FAE cloud is formed, it must be detonated by exploding an explosive charge or its equivalent within the boundaries of the cloud. This charge is referred to as the SE (second event) charge and the associated dispersal system is called the SE system. The specific requirements for the SE charge, such as its size, delay and spatial position are critical parameters which must be determined in order to provide an FAE device with the proper high explosive source.
The location of the FAE cloud, relative to some reference point such as location of the FAE device at the time the fuzing system is initiated, will depend upon the many variables of the FAE device as well as upon terminal aerodynamic conditions, such as speed and orientation, and upon proximity of the ground plane. A typical cloud will form into a distorted torus shape which has an outer diameter of roughly 60 feet and its thickness may be about 20 feet. The center plane of the cloud may be displaced along the line of flight several tens of feet. The cloud will generally have a central hole along the line of flight of about 10 feet in diameter. Finally, the ground plane will further distort the cloud locally. The position of the FAE cloud at or near its terminal size will be reached about 100 milliseconds after the burster charge is detonated.
The SE system must deliver the SE package or charge to an appropriate position within the cloud such that, when the SE charge detonates, the cloud will detonate in a reliable fashion. Reliability of the placement and performance of the SE package, together with variability of the characteristics of the FAE cloud, requires that a plurality of SE packages are needed. Spatial and time delay requirements indicate that the SE packages will have to be launched from the FAE device with a sideward velocity of the order of 200 fps. The flight velocity which can range from 400 to 1000 fps must be approximately nullified. Thus, the SE packages must be accelerated primarily rearward in a controlled fashion from the FAE device at a velocity approximately equal to the device's flight velocity. Furthermore, this launching process must be accomplished during the period in which the FAE device is exploding. Since large deformation of the FAE device will occur within 1 msec, the SE packages must be launched in such a period of time. Any interaction between these two processes must be considered in the design of the SE system.
The need of a speed controlled second event system becomes apparent as the ranges of the terminal parameters are broadened. It becomes essential to alter the retrolaunch conditions for widely varying terminal velocities and incident angles in order to still deploy at least one SE detonator within the resultant detonable cloud volume. The implementation of a speed control system for the second event task requires first that the magnitude of the flight velocity be adequately sensed and secondly that certain retrolauncher parameters be adjusted so that the desired burst region can be reached. It also is necessary to have available some power source with which to make the needed adjustments. The total pressure which the FAE device possesses as a result of its motion represents both a strong indicator of its flight velocity as well as a suitable source of energy. The azimuthal orientation of the device as well as the angle of incidence of the flight path with the ground plane are, for practical consideration indetectable and must therefore be considered to be random in nature.